Auto merge of #6589 - giraffate:add_notes_of_prioritization_labels_to_doc, r=flip1995
Auto merge of #6589 - giraffate:add_notes_of_prioritization_labels_to_doc, r=flip1995

Add notes of prioritization labels to doc

Refer to https://rust-lang.zulipchat.com/#narrow/stream/257328-clippy/topic/New.20prioritization.20labels.

changelog: none

aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust